Synchronous circuit interrupter



July 13, 1937. L. E. NECHQLS SYNCHRONOUS CIRCUIT INTERRUPTER Filed April 20, 1951 4 Sheets-Sheet l lizaweaa/af lieoa'zaz dfiizvwwlg y Ad/ mv m J ly 1937- L, E. McHoLs fi fi SYNCHRONOUS CIRCUIT INTERRUPTER Filed April 20, 1951 4 Sheets-Sheet 2 ffizg Jfily 13, 1937. L 0 5 2,086,876

SYNCHRONOUS CIRCUIT INTERRUPTER Filed April 20, 1931 4 Sheets-Sheet 3 July 13, 1937. L. E. NICHOLS SYNCHRONOUS CIRCUIT INTERRUPTER Filed April 20, 1931 4 Sheets-Sheet 4 -Patented July 13, 1937 UNITED STATES PATENT OFFICE Leonard E. Nichols, Bay City,

Mich, assignor to Thomson-Gibb Electric Welding Company, Lynn, Mass, a corporation of -Massachusetts Application April 20, 193i, Serial No. 53i,46d

,14 Claims.

This invention relates to current interrupting devices intended more particularly for electric welding machines, and consists in the provision of a synchronously operated circuit breaking device adapted to break a circuit carrying an alternating current at some suitable point in the alternating current wave under conditions giving a quick, clean break and with substantial elimination of arcing and burning at the contacts.

The use of a synchronously driven circuit breaker, as, for example, one driven from a synchronous motor, has certain advantages, since the breaker by appropriate adjusting devices may be so timed as to act at approximately zero current value, where the tendency to are at the contacts is at a minimum.

Such a circuit breaking device, adjusted to efiect the break at approximately zero value of the current, if caused to move rapidly in eiiecting the break, as by being driven at high speed by a synchronous motor, will be adequate to suppress any serious arcing tendency at the contacts, even when used with heavy welding primary loads. If the break, however, is effected at thehigh speed necessary to secure satisfactory results, as, for example, by the direct drive from. the shaft of a synchronous motor, the periodicity of the interruptions or the number of breaks per minute will ordinarily be at too high a rate to be usable for many classes of welded work. Furthermore, the interruptions per minute should be preferably-adjustable to suit different types of work.

If it is attempted to vary or reduce the number of interruptions per minute by the interposition of speed reducing mechanism between the breaking device and the motor or other synchronous high speed agency employed, the breaking speed of the breaking device is lowered, the breaking action is correspondingly prolonged and the benefit of a quick break at zero value is sacrificed, tending to make the interrupting mechanism unsuitable with currents of high wattage.

In the illustrative embodiment of the invention a current interrupting mechanism is provided in which the break at rapidly moving breaking device actuated by a high speed synchronous agency. Preferably the breaking device is actuated by or through the rotation of a synchronous motor, its action being adjusted to take place at the time when the current is at or near its zero value so that a quick break may be had under all conditions of use. With this there is combined suitably coordinated controlling mechanism to related as to render the contacts is effected by a (GE. Will-91) the breaking device ineffective to interrupt the ircuit for one or more of its cycles of operation, whereby the rate per unit of time at which the interruptions take place becomes less than the rate at which the breaker is driven, same time the breaking device, when efie'ctive, moves always at the same high rate of breaking speed.

While the present invention in a wide variety of mechanical trative purposes, I have herein shown a breakin device, adapted to open the contacts, in the form of a breaker cam driven directly by the shaft of a synchronous motor. i'he latter is operated in synchronism with absolute speed in revolutions per minute being high enough to provide the desired quick breaking movemen By way of example, theinotor may be run at a speed of 1800 revolutions per may be embodied the welding current, its 1 while at the 5 forms, for illusl0 minute, providing for i800 rotations of the break- 20 er earn per minute and for a very quick breaking movement when the breaker is allowed to act. With this there is associated also a breaking control member, which is herein also in the form of a cam and driven also relation to the breaking device but at such a speed that it serves to render the breaking cam inefiective to interrupt the circuit during one or more revolutions thereof. By way of illustraby the motor in timed 25 tion, the breaker control cam may be driven at 30 some sub-multiple of cam, such as one-sixth the speed of the latter, or at 300 revolutions per minute, so that interruptions may occur only on each revolution of the breaker control cam, but each one taking place under the high speed movement of the, breaking device.

In current interrupting devices for welding machines some particular ratio of current dwell to current interruption for each interruption cycle, such, for example, as a ratio of 2 to l, is normally aimed at, but for certain'types of welding work not only should there be provision for adjusting the number of interruption cycles per minute but it may be desirable to vary for each interruption cycle the ratio of current dwell to length of current interruption. In resistance seam welding on heavier gauge material, for example, the ratio of current dwell should preferably be greater than two to one and a lower number of breaks per minute than normal be employed. In the described embodiment of the invention, not only may the number of interruption the speed 01' the breaker speed of the breaker control device, but irrespective of the rate of interruption cycles to which the mechanism may be adjusted, the desired length of current dwell may be maintained for each cycle and different ratios of current dwell may be secured.

This and other objects of the invention will be best understood by reference to the following description when taken in connection with the accompanying illustrations showing one specific embodiment thereof, while its scope will be more particularly pointed out in the appended claims.

In the drawings:

Fig. 1 is a front elevation, partly broken away and looking toward the end of the synchronous driving motor, showing a circuit interrupting device embodying one form of the invention;

Fig. 2 is a sectional, side elevation of the device shown in Fig. 1, taken on the broken line 22;

Fig. 3 is a diagrammatic view showing the relation of the interrupter tothe primary circuit of an electric welding machine;

Fig. 4 is a side elevation of the same device, viewed from the right in Fig. 1 or on the opposite side from Fig. 2; and

Fig. 5 is a diagram showing, for several diiferent rates of interruption cycles, the relative action of the several cams in effecting the circuit break and in controlling the length of current dwell.

Referring to the drawings and to the embodiment of the invention there submitted for illustrative purposes, the interrupter (Figs. 1 and 3) comprises relatively movable contacts, herein a stationary contact I 1 having a contacting face of copper or other conductive material and of 'substantial area and opposed to a similar but movable contact l3 which is normally held against the contact H to complete the circuit therethrough but may be retracted to separate the contacts and break the circuit.

To illustrate merely one application of the interrupting device to the welding circuit of an electric welding machine, the interrupting contacts H and I3 may be in series (Fig. 3) with an alternating current supply circuit l5, from which is operated the synchronous motor I! adapted to actuate the movable contact of the interrupter, the circuit l5 also supplying the primary is of the welding transformer, the secondary 2| of which is connected to supply a low voltage current of high amperage to the welding electrodes 23.

The interrupter may be soconnected as to completely open the primary circuit, with the complete stoppage of all current in both the primary and secondary circuits, or so connected that, by its circuit-interrupting action, it cuts down the current flow in the primary to such a point that no effective welding current flows through the secondary circuit to the welding electrodes. By way of example, in many cases, particularly where heavy Welding loads or high voltages are employed, it may be desirable to provide a resistance 24 (Fig. 3) placed in shunt about the interrupter contacts to suppress any possible arcing at the contacts. Such resistance, however, should be of suitable amount to suppress any substantial effective welding current at the electrodes when the interrupter contacts are open, a

resistance of approximately 20 ohms being ordinarily sufficient. apparently is to bring the voltage and current curves more nearly in phase when the break oc curs at the contact points so-that the benefit of a break at zero current value is fully availed pf.

The effect of such a resistance It will be understood, therefore, that where interruptions or breaks in the circuit or the current are hereinafter mentioned, interruptions in the breaker circuit are referred to, whether that circuit is the main circuit or a shunt circuit, the effect of the break, however, being to interrupt or cause the cessation of an effective welding current in the secondary.

Referring to Figs. 1, 2, and 3, the contacts II and [3 are supported in and insulated from the holders 25 and 21 respectively, the holder 25 be ing connected to the arm 29 and the holder 21 to the arm 3|. The contacts may be water cooled by the piping connections 33 if desired.

To support the contact arms 29 and 3| and other elements of the mechanism, there is provided a supporting plate 35 having a laterally extending shell or sleeve 31 clamped on and supported by a part 39 (Fig. 2) of the motor frame which is concentric with the motor shaft. This sleeve is split at 4| (Fig. 1) and provided with a clamping screw 43 so that, for a purpose to be described, the supporting plate with all parts mounted thereon may be turned to any desired angular position of adjustment about an axis coinciding with the axis of the motor shaft and there fixedly clamped in position. The supporting plate also carries the necessary electrical connections for the contacts, the latter being connected (Fig. 4) by flexible strips of conductive metal 44 to permit their necessary opening and closing movements.

The depending connecting arm 29 for the fixed contact II is pivotally mounted at its lower end upon a pin 45 (Fig. 1) extending laterally and outwardly from the supporting plate 35, the arm being provided at an upper intermediate point with a slotted portion 41 through which the arm is clamped by the bolt 49 to a lateral lug on the plate 35, this providing for the adjustment of the arm and its contactwithin certain limits to any required fixed position.

The depending arm 3i for the movable contact I 3 (Fig. 1) is mounted on and guided by two pins extending outwardly and laterally from the plate 35, the upper one 5| of which engages a transverse slotted portion 53 of the arm, and the lower one 55 a similar slotted portion 51. This arm, which, under the action of the high speed breaking cam, functions as the contact breaking lever, thus has a free or floating movement on the pins within the limits of the slots. A spring 53 is interposed between a lug 6| on the movable lever arm3l and a threaded adjusting member 63 mounted in a bracket 65 extending from the supporting plate, so that the spring tends to force the upper end of the lever arm 3| to the left (as viewed in Fig. 1) or toward a contact closing position. Similarly, an adjustable spring 61 is interposed between the lower end of the arm 5| and a laterally extending bracket 69 on the supporting plate, serving to force the lower end of the arm to the right (as viewed in Fig. 1).

The lever arm 31 between the two slotted portions 53 and 55 is provided with a cam engaging plate H which faces in close relationship the periphery of a cam member mounted on the motor shaft, the construction and function of which will be shortly explained. The lower end of the lever arm 3] below the slotted portion 53 is provided with a similar cam engaging plate 13 which is forced by the spring 61 against the periphery of a breaker control cam 15, the latter secured to a sleeve Ti journaled on a fixed support l9 extending outwardly and laterally from the supporting plate.

When the cam plate 13 on the lower end of the arm 3| bears upon the lower part of the periphery of the cam 15, the arm is held in a position which causes the raised part of 'the motor shaft cam member to clear the face of the opposed cam plate H, so that no contact-opening movement of the arm can take place under these conditions. Nor can any opening movement of the arm occur when the raised part of the periphery of the cam 15 moves the lower end of the lever 31 to the left (Fig. 1), unless the raised part of the motor shaft cam member also engages the cam plate H during the time the lever arm 3! occupies this position. When, however, there is a coincident engagement of the raised portions of both cams with their respective cam plates, the motor shaft cam serves to swing the lever arm outwardly or to the right (Fig. l), the cam l5 serving as a fulcrum about which this movement takes place and resulting in an opening. movement of the movable contact, which is held in its open position so long'as the coincident action of the two cams persists.

Referring now to the motor shaft cam member, the latter is composed of two earns, a circuit breaking cam 8| and a hold out cam 83 (the function of which will be later explained) arranged side by side (Fig. 2), and cooperatively related each to the cam plate H. The circuit breaking cam 8| is keyed or otherwise fixedly secured to the motor shaft 85 to rotate therewith at the full high motor speed, and the cam 83 is keyed or otherwise fixedly secured to a sleeve 81, the latter adapted to turn freely about the motor shaft, the sleeve and its cam 83 being driven at a different speed from that of the cam 8|, and herein at the same speed as that of the breaker control cam 15. For that purpose the sleeve 11 carrying the breaker control cam 115 has fixed thereon the sprocket wheel 89 (Fig. 2) which drives the sleeve 8'! and its associated cam 83 through the connecting driving chain M (Fig. l) and sprocket wheel 93, the latter being fixed on the sleeve 81 and having the same pitch as that of the sprocket wheel 89. In Fig. 2 the cams are shown in a somewhat different angular position from Fig. 1 in order to show the raised parts on cams 8| and 83 in engagement with the cam plate ll.

It will be seen that the breaker cam 8|, which is here relied on to effect the initial high speed breaking movement of the contacts, is driven directly by the motor at a relatively high rate of speed, so thata quick break is assured, and, furthermore, is synchronously related in its operation to the current wave in the primary circuit so that, by the rotative adjustment of the supporting plate with the entire supported mechanism about the motor frame member 39, the break may be adjusted and fixed to take place with reasonable certainty at a time which closely approximates the zero value of the current, and such adjustment may be readily secured irrespective of the rate of alternations in the current wave or the relation of the latter to the absolute rate of speed of the motor so long as the latter is synchronously operated. I

As an illustrative example merely, if the speed of the motor is assumed to be 1800 revolutions per minute, and the mo or is operated on a 60 cycle alternating current circuit, the breaker cam is then driven at a high rate of speed and presents 1800 times each minute the raised portion of its periphery to the cam plate II and in position to effect a breaking movement of the contact arm 3|, dependent on the coincident action of the breaker control cam 15-.

To provide for a lesser number of interruptions per minute than is represented by the rotational rate of the breaker cam 8|, the latter is rendered ineffective for one or more of its cycles of operation by the action of the breaker control cam 15,

-which latter is driven in timed relation to the breaker cam but at such a speed that coincidence of action of the two cams on the breaking lever arm occurs at a rate less than the rate of rotation of the breaker cam, the two cams being so related, however, that the breaking movement of the lever arm 3i is in each case eifected under the high speed action of the breaker cam.

In the illustrated embodiment of the invention, the breaker control cam T5 is driven at a speed whic l. is a sub-multiple, and in the illustrated instance one-sixth, of the speed of the motor shaft and breaker cam, provision being made, however, whereby the speed of the breaker cam may be adjusted to'some other sub-multiple of that of the breaker cam.

For this purpose, the motor shaft 85 has secured at its outer end the driving pinion 85 which meshes with an idler gear 91 journaled upon the shaft 99 which is secured to and extends laterally from the supporting plate 35. The gear 91 in turn meshes with a gear l0! which is keyed or otherwise fixedly secured to the sleeve 11 carrying the breaker control cam 15. The gears 95 and till are herein so proportioned that the gear lill and the breaker control cam make one revolution for each six revolutions of the breaker cam, so that the breaker control cam conditions the lever arm to be moved by the breaker cam for an interval occurring once during each six revolutions of the breaker cam, or, in the case of the speed of 1800 revolutions per minute assumed for the motor, at a rate of 300 times per minute. This rate, however, may be varied to suit the requirements in any particular case by changing the gearing ratio between the gears 95 and NH, provision being made in the illustrative embodiment for substituting another gear of different dimensions for the gear 95 to produce such changed gearing ratio. For this purpose the shaft 99 carrying the idle gear is-clamped in an arcshaped slot 563 on the supporting plate 35, the slot being concentric with the axis of the gear llll, so that the idle gear 2'? may be moved to accommodate various gears of larger or smaller radius to be substituted for the gear 95, the latter, however, preferably providing in each case for the rotation of the gear llll and cam l5 at a speed which is a sub-multiple of the speed of the breaker cam 81.

It is desirable that each cycle of operation of the interrupting device should comprise an interval in which the circuit is continuously open, followed by an interval during which the circuit is continuously closed, the interval of current dwell being ordinarily about twice the interval of current interruption. Herein the hold-out cam, which it will be observed is driven at the same speed as the breaker control cam 15, provides means whereby the interval during which the circuit is continuously open may be properly proportioned to the interval during which it is continuously closed, its employment also avoiding successive breaks in the same cycle of operation of the interrupter during the interval when the raised peripheral portion of the control cam is engaged with the cam plate 13, which successive breaks might follow where the cam 15 is driven at a speed relatively low as compared with that of the cam 8!.

The hold-out cam accordingly functions to hold the lever arm 3| in contact-opening position after it has been initially moved to that position by the high speed breaker cam 8| during the coincident action of the breaker control cam I5, and to hold it in that position after the breaker cam has become disengaged from its cam plate 3| and during the continued coincident action of the cam I for such continuous interval as may be required.

The cooperative action of the three cams, as provided for in the illustrative embodiment of the invention, will be readily understood from the diagram in Fig. 5, in which A represents a development of the breaker cam 8|. for six successive cycles of its rotation, C C C the peripheral rise on the cam being represented at I03 and herein assumed to extend for approximately 145 of the cam periphery.

At B is represented a development of the holdout and breaker control cams 83 and I5, respectively, showing the timed relationship of the action of these cams to the action of the breaker cam when the former are driven at a speed onesixth the. speed of the breaker cam. -The peripheral rise in the hold-out cam is represented at I05 and is herein assumed to extend for approximately 120 or one-third of the cam periphery. The peripheral rise on the breaker control cam is represented at I01 and is herein assumed to extend for-approximately 140 of the cam periphery.

With the breaker cam mounted directly on the motor shaft and driven at a speed of 1800 R. P. M., the speed of the breaker control and hold-out 'cams will be 300 R. P. M., and these cams afiord means whereby the interruptions of the circuit may be made to occur periodically at the rate of 300 per minute. Comparing the relation of the cams in thediagrams A and B, the contact carrying arm 3i will be actuated at the point C under the high speed action of the breaker cam rise I03, the arm having been subjected to the action of the breaker control cam rise I01 just immediately preceding the action thereon of the cam 8I. Before the rapidly moving cam I03 falls away from the contact carrying arm 3|, the rise I05 of the more slowly moving hold-out cam has engaged that arm and continues to maintain the latter in a contact-opening position after the cam rise I03 has receded from the arm. This action of the hold-out cam continues during the continuance of the coincident action of the breaker control cam, which latter persists until approximately the point C is reached in the cycle of operation. Thereupon the breaker control cam rise I01 drops away from the contact carrying arm, the latter is forced back again to its con tact-closing position, and the current as reestablished continues to flow until the breaker cam has completed the. four succeeding revolutions, when the same operation is again repeated. The interval in this cycle during which the current is interrupted is represented by the shaded area I09, and in the assumed case is so proportioned as to comprise about one-third of the interruption cycle, the circuit being, interrupted for one-third and closed for two-thirds of that time, and the break taking place at the rate of 300 times per minute or once for each revolution of the breaker cam.

By suitably proportioning the cam rise on the hold-out cam or on the breaker control cam, the ratio of the interruption period to the current dwell period may be either shortened or lengthened to any desired extent.

As previously stated, by changing the ratio of the gearing between the motor shaft and the breaker control cam I5 the rate of interruptions may be varied to any sub-multiple of the speed rate of the breaker cam.

' At C the relationship of the hold-out cam and the breaker control cam to the breaker cam (represented at A) is shown where a speed reduction of four to one is employed, providing, at the assumed speed of 1800 R. P. M. for the breaker cam, a speed of 450 R. P. M. for the other two cams, the break then occurring at each fourth revolution of the breaker cam or at the rate of 450 circuit interruptions per minute.

In D a similar diagram is shown where the speed reduction is assumed-to be three to one, the breaks occurringat 600 per minute, and at E a further similar diagram where the speed reduction is assumed to be two to one, the breaks here occurring at the rate oi 900 per minute.

While I have herein shown and described for the purpose of illustration the details of one specific embodiment of the invention, it is to be understood that extensive deviations or changes may be made in the illustrated form and that breaking elements of widely varying types may be employed, all without departing from the spirit of the invention.

I claim:

1. A current interrupter for electric welding comprising a synchronously driven, high speed, actuating device with means actuated thereby to effect a quick break in the alternating current circuit at the approximate time of zero current value, and means to adjust the rate of current interruptions while maintaining substantially the same speed of the actuating device to obtain a rate of current interruption less than that at whichthe cycle of operations of theactuating device takes place.

2. The combination with an interrupter for breaking an alternating current circuit, of a synchronous motor operated from said circuit, means driven from said motor to actuate said interrupter at motor speed, means to cause in- .terruptions to take place at a rate which is a sub-multible of the motor speed, and means for adjusting said actuating means to cause the interruption to take place at approximately zero current value.

3. The combination with an interrupter for breaking an alternating current circuit, of a synchronous motor operated from said circuit, means driven from said motor to actuate said interrupter at a speed not less than the motor speed, and means to cause the interruption to take place at a rate which is a sub-multiple of the rate at which the actuating means is operated.

4. The combination with an interrupter for breaking an alternating current circuit, of a synchronous motor operated from said circuit, an interrupter actuating device driven from said motor at the motor speed, said actuating device being adapted to cause the interruption of the circuit to take place at approximately zero current value, and means to cause the interruptions to take place at a rate which is a sub-multiple ot the rate at which the actuating device is oper ated.

5. A circuit interrupting device for electric welding comprising a synchronous motor'operated from an alternating current circuit, a circult breaking device, an actuating device theresynchronous motor, a

motor, a breaking member actuated by the cam, to prolong the interval the motor, a

for adapted to efiect a succession of quick breaks in the circuit, means for driving. said actuating device at a speed not less than the motor speed,

and means to establish a rate of interruptions at a rate other than that at which the cycle of operations of the actuating device takes place. 6. A circuit interrupter for electric welding comprising a circuit breaking device, a synchronously operated, high speed, actuating device for said circuit breaker adapted to effect a repeated succession of quick breaks in an alternating current circuit at the approximate time of zero current value, and separate means acting between successive periodic actions of the actuating device to hold the circuit open.

'7. The combination with an interrupter for breaking an alternating current circuit, of a breaker cam driven by the breaker cam to break the circuit, and means to establish a rate at which the interruptions take place less than the rate of rotation of the cam.

8. The combination with an interrupter for breaking an alternating current circuit, of a synchronous motor, a breaker cam driven by breaking member actuated by the breaker cam to break the circuit, and a breaker control cam also driven by the motor and related to the breaking member to render the breaker cam ineffective to break the circuit for one or more revolutions thereof.

9. A circuit interrupter for electric welding comprising a synchronous motor, a high speed breaker cam driven by the motor, a breaking member actuated by the breaker cam to break the circuit, and a second cam actuating the breaking member, also driven synchronously by the motor but at a slower speed than the breaker of break following the action of the breaker cam.

10. The combination with an interrupter for breaking an alternating current circuit, of a synchronous motor, a breaker cam driven by the motor, a breaking member actuated by the breaker cam to break the circuit, a breaker control cam also driven by the motorand related to the breaking member to render the breaker cam ineffective to break the circuit for one or more revolutions thereof, and a hold-out cam to hold the circuit open for a prolonged interval af er the breaker cam is actuated.

' the circuit, and a hold-out cam also acting on the breaker device to prolong the interval of break following the action of breaker cam.

12. The combination with circuit interrupting contacts for an alternating current circuit, of a synchronous motor, a breaker cam driven by the motor, a breaking member operatively related to the breaker cam to be moved by the latter to effects. succession of quick breaks in said circuit, and a breaker control cam also driven by said motor but at a speed which'is a sub-multiple of the speed of the breaker cam, said breaker control cam being operatively related to said breaking member to withdraw the latter from circuit breaking engagement with said breaker cam for a portion of each revolution of said breaker control cam, thereby to establish a rate of interruptions at a rate less than that of the rotation of said breaker cam.

13. In a circuit interrupting device for an alternating current circuit, the combination with a synchronous motor, of a supporting frame mounted on the frame of the motor concentric with the shaft thereon and rotatably adjustable a about the axis of said shaft, a breaker cam on the motor shaft, relatively movable circuit breaking contacts carried by said supporting frame, a reciprocatory breaking member connected to one of said contacts and'having a floating connection to said frame with means for normally holding said contacts closed, said member being operatively related to the breaking cam but normally withdrawn from the path thereof, a breaker control cam also mounted on said supporting frame and operatively related to said breaking member and adapted to move said member into and out of the path of said breaker cam on each rotation of the breaker control cam, and speed reduction driving connections between said motor shaft and said breaker l control cam comprising a driving gear on the motor shaft and a driven gear and intermediate idler gear on the supporting frame, whereby a rate of interruptions may be established less than that of the motor speed, and through adjustment of the supporting frame about the axis of the motor shaft successive breaks may be made to take place at approximately zero current value.

14. A current interrupter for an alternating current circuit, the same comprising, in combination, circuit breaking contacts, a Synchronously driven, high speed actuating device adapted to act on said contacts and effect a succession of repeated quick breaks in said circuit, means to adjust said device to cause the break to occur at the approximate time of zero current value, and controlling means for said actuatine device to establish the rate of interruptions at a rate less than that at which the cycle of operations of the actuating device takes place.

LEONARD E. NICHOIS. 

